base64.java

基于Jabber协议的即时消息服务器

package org.jivesoftware.util;

/**
 * Encodes and decodes to and from Base64 notation. <p/> <p/> Change Log:
 * </p>
 * <ul>
 * <li>v2.1 - Cleaned up javadoc comments and unused variables and methods.
 * Added some convenience methods for reading and writing to and from files.</li>
 * <li>v2.0.2 - Now specifies UTF-8 encoding in places where the code fails on
 * systems with other encodings (like EBCDIC).</li>
 * <li>v2.0.1 - Fixed an error when decoding a single byte, that is, when the
 * encoded data was a single byte.</li>
 * <li>v2.0 - I got rid of methods that used booleans to set options. Now
 * everything is more consolidated and cleaner. The code now detects when data
 * that's being decoded is gzip-compressed and will decompress it automatically.
 * Generally things are cleaner. You'll probably have to change some method
 * calls that you were making to support the new options format (<tt>int</tt>s
 * that you "OR" together).</li>
 * <li>v1.5.1 - Fixed bug when decompressing and decoding to a byte[] using
 * <tt>decode( String s, boolean gzipCompressed )</tt>. Added the ability to
 * "suspend" encoding in the Output Stream so you can turn on and off the
 * encoding if you need to embed base64 data in an otherwise "normal" stream
 * (like an XML file).</li>
 * <li>v1.5 - Output stream pases on flush() command but doesn't do anything
 * itself. This helps when using GZIP streams. Added the ability to
 * GZip-compress objects before encoding them.</li>
 * <li>v1.4 - Added helper methods to read/write files.</li>
 * <li>v1.3.6 - Fixed OutputStream.flush() so that 'position' is reset.</li>
 * <li>v1.3.5 - Added flag to turn on and off line breaks. Fixed bug in input
 * stream where last buffer being read, if not completely full, was not
 * returned.</li>
 * <li>v1.3.4 - Fixed when "improperly padded stream" error was thrown at the
 * wrong time.</li>
 * <li>v1.3.3 - Fixed I/O streams which were totally messed up.</li>
 * </ul>
 * <p/> <p/> I am placing this code in the Public Domain. Do with it as you
 * will. This software comes with no guarantees or warranties but with plenty of
 * well-wishing instead! Please visit <a
 * href="http://iharder.net/base64">http://iharder.net/base64</a> periodically
 * to check for updates or to contribute improvements.
 * </p>
 * 
 * @author Robert Harder
 * @author [e-mail]
 * @version 2.1
 */
class Base64 {

	/* ******** P U B L I C F I E L D S ******** */

	/**
	 * No options specified. Value is zero.
	 */
	public final static int NO_OPTIONS = 0;

	/**
	 * Specify encoding.
	 */
	public final static int ENCODE = 1;

	/**
	 * Specify decoding.
	 */
	public final static int DECODE = 0;

	/**
	 * Specify that data should be gzip-compressed.
	 */
	public final static int GZIP = 2;

	/**
	 * Don't break lines when encoding (violates strict Base64 specification)
	 */
	public final static int DONT_BREAK_LINES = 8;

	/* ******** P R I V A T E F I E L D S ******** */

	/**
	 * Maximum line length (76) of Base64 output.
	 */
	private final static int MAX_LINE_LENGTH = 76;

	/**
	 * The equals sign (=) as a byte.
	 */
	private final static byte EQUALS_SIGN = (byte) '=';

	/**
	 * The new line character (\n) as a byte.
	 */
	private final static byte NEW_LINE = (byte) '\n';

	/**
	 * Preferred encoding.
	 */
	private final static String PREFERRED_ENCODING = "UTF-8";

	/**
	 * The 64 valid Base64 values.
	 */
	private final static byte[] ALPHABET;

	private final static byte[] _NATIVE_ALPHABET = /*
													 * May be something funny
													 * like EBCDIC
													 */
	{ (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F',
			(byte) 'G', (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K',
			(byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P',
			(byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U',
			(byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z',
			(byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e',
			(byte) 'f', (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j',
			(byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', (byte) 'o',
			(byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't',
			(byte) 'u', (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y',
			(byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3',
			(byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8',
			(byte) '9', (byte) '+', (byte) '/' };

	/** Determine which ALPHABET to use. */
	static {
		byte[] __bytes;
		try {
			__bytes = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
					.getBytes(PREFERRED_ENCODING);
		} // end try
		catch (java.io.UnsupportedEncodingException use) {
			__bytes = _NATIVE_ALPHABET; // Fall back to native encoding
		} // end catch
		ALPHABET = __bytes;
	} // end static

	/**
	 * Translates a Base64 value to either its 6-bit reconstruction value or a
	 * negative number indicating some other meaning.
	 */
	private final static byte[] DECODABET = { -9, -9, -9, -9, -9, -9, -9, -9,
			-9, // Decimal 0 - 8
			-5, -5, // Whitespace: Tab and Linefeed
			-9, -9, // Decimal 11 - 12
			-5, // Whitespace: Carriage Return
			-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 14 -
																// 26
			-9, -9, -9, -9, -9, // Decimal 27 - 31
			-5, // Whitespace: Space
			-9, -9, -9, -9, -9, -9, -9, -9, -9, -9, // Decimal 33 - 42
			62, // Plus sign at decimal 43
			-9, -9, -9, // Decimal 44 - 46
			63, // Slash at decimal 47
			52, 53, 54, 55, 56, 57, 58, 59, 60, 61, // Numbers zero through nine
			-9, -9, -9, // Decimal 58 - 60
			-1, // Equals sign at decimal 61
			-9, -9, -9, // Decimal 62 - 64
			0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, // Letters 'A'
															// through 'N'
			14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, // Letters 'O'
															// through 'Z'
			-9, -9, -9, -9, -9, -9, // Decimal 91 - 96
			26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, // Letters 'a'
																// through 'm'
			39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, // Letters 'n'
																// through 'z'
			-9, -9, -9, -9 // Decimal 123 - 126
	/*
	 * ,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 127 - 139
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 140 - 152
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 153 - 165
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 166 - 178
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 179 - 191
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 192 - 204
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 205 - 217
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 218 - 230
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9, // Decimal 231 - 243
	 * -9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9,-9 // Decimal 244 - 255
	 */
	};

	// I think I end up not using the BAD_ENCODING indicator.
	// private final static byte BAD_ENCODING = -9; // Indicates error in
	// encoding
	private final static byte WHITE_SPACE_ENC = -5; // Indicates white space in
													// encoding

	private final static byte EQUALS_SIGN_ENC = -1; // Indicates equals sign in
													// encoding

	/**
	 * Defeats instantiation.
	 */
	private Base64() {
	}

	/* ******** E N C O D I N G M E T H O D S ******** */

	/**
	 * Encodes up to the first three bytes of array <var>threeBytes</var> and
	 * returns a four-byte array in Base64 notation. The actual number of
	 * significant bytes in your array is given by <var>numSigBytes</var>. The
	 * array <var>threeBytes</var> needs only be as big as <var>numSigBytes</var>.
	 * Code can reuse a byte array by passing a four-byte array as <var>b4</var>.
	 * 
	 * @param b4
	 *            A reusable byte array to reduce array instantiation
	 * @param threeBytes
	 *            the array to convert
	 * @param numSigBytes
	 *            the number of significant bytes in your array
	 * @return four byte array in Base64 notation.
	 * @since 1.5.1
	 */
	private static byte[] encode3to4(byte[] b4, byte[] threeBytes,
			int numSigBytes) {
		encode3to4(threeBytes, 0, numSigBytes, b4, 0);
		return b4;
	} // end encode3to4

	/**
	 * Encodes up to three bytes of the array <var>source</var> and writes the
	 * resulting four Base64 bytes to <var>destination</var>. The source and
	 * destination arrays can be manipulated anywhere along their length by
	 * specifying <var>srcOffset</var> and <var>destOffset</var>. This method
	 * does not check to make sure your arrays are large enough to accomodate
	 * <var>srcOffset</var> + 3 for the <var>source</var> array or
	 * <var>destOffset</var> + 4 for the <var>destination</var> array. The
	 * actual number of significant bytes in your array is given by
	 * <var>numSigBytes</var>.
	 * 
	 * @param source
	 *            the array to convert
	 * @param srcOffset
	 *            the index where conversion begins
	 * @param numSigBytes
	 *            the number of significant bytes in your array
	 * @param destination
	 *            the array to hold the conversion
	 * @param destOffset
	 *            the index where output will be put
	 * @return the <var>destination</var> array
	 * @since 1.3
	 */
	private static byte[] encode3to4(byte[] source, int srcOffset,
			int numSigBytes, byte[] destination, int destOffset) {
		// 1 2 3
		// 01234567890123456789012345678901 Bit position
		// --------000000001111111122222222 Array position from threeBytes
		// --------| || || || | Six bit groups to index ALPHABET
		// >>18 >>12 >> 6 >> 0 Right shift necessary
		// 0x3f 0x3f 0x3f Additional AND

		// Create buffer with zero-padding if there are only one or two
		// significant bytes passed in the array.
		// We have to shift left 24 in order to flush out the 1's that appear
		// when Java treats a value as negative that is cast from a byte to an
		// int.
		int inBuff = (numSigBytes > 0 ? ((source[srcOffset] << 24) >>> 8) : 0)
				| (numSigBytes > 1 ? ((source[srcOffset + 1] << 24) >>> 16) : 0)
				| (numSigBytes > 2 ? ((source[srcOffset + 2] << 24) >>> 24) : 0);

		switch (numSigBytes) {
		case 3:
			destination[destOffset] = ALPHABET[(inBuff >>> 18)];
			destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
			destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
			destination[destOffset + 3] = ALPHABET[(inBuff) & 0x3f];
			return destination;

		case 2:
			destination[destOffset] = ALPHABET[(inBuff >>> 18)];
			destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
			destination[destOffset + 2] = ALPHABET[(inBuff >>> 6) & 0x3f];
			destination[destOffset + 3] = EQUALS_SIGN;
			return destination;

		case 1:
			destination[destOffset] = ALPHABET[(inBuff >>> 18)];
			destination[destOffset + 1] = ALPHABET[(inBuff >>> 12) & 0x3f];
			destination[destOffset + 2] = EQUALS_SIGN;
			destination[destOffset + 3] = EQUALS_SIGN;
			return destination;

		default:
			return destination;
		} // end switch
	} // end encode3to4

	/**
	 * Serializes an object and returns the Base64-encoded version of that
	 * serialized object. If the object cannot be serialized or there is another
	 * error, the method will return <tt>null</tt>. The object is not
	 * GZip-compressed before being encoded.
	 * 
	 * @param serializableObject
	 *            The object to encode
	 * @return The Base64-encoded object
	 * @since 1.4
	 */
	public static String encodeObject(java.io.Serializable serializableObject) {
		return encodeObject(serializableObject, NO_OPTIONS);
	} // end encodeObject

	/**
	 * Serializes an object and returns the Base64-encoded version of that
	 * serialized object. If the object cannot be serialized or there is another
	 * error, the method will return <tt>null</tt>. <p/> Valid options:
	 * 
	 * <pre>
	 *    GZIP: gzip-compresses object before encoding it.
	 *    DONT_BREAK_LINES: don't break lines at 76 characters
	 *      &lt;i&gt;Note: Technically, this makes your encoding non-compliant.&lt;/i&gt;
	 * </pre>
	 * 
	 * <p/> Example: <code>encodeObject( myObj, Base64.GZIP )</code> or <p/>
	 * Example:
	 * <code>encodeObject( myObj, Base64.GZIP | Base64.DONT_BREAK_LINES )</code>
	 * 
	 * @param serializableObject
	 *            The object to encode
	 * @param options
	 *            Specified options
	 * @return The Base64-encoded object
	 * @see Base64#GZIP
	 * @see Base64#DONT_BREAK_LINES
	 * @since 2.0
	 */
	public static String encodeObject(java.io.Serializable serializableObject,
			int options) {
		// Streams
		java.io.ByteArrayOutputStream baos = null;
		java.io.OutputStream b64os = null;
		java.io.ObjectOutputStream oos = null;
		java.util.zip.GZIPOutputStream gzos = null;

		// Isolate options
		int gzip = (options & GZIP);
		int dontBreakLines = (options & DONT_BREAK_LINES);

		try {
			// ObjectOutputStream -> (GZIP) -> Base64 -> ByteArrayOutputStream
			baos = new java.io.ByteArrayOutputStream();
			b64os = new Base64.OutputStream(baos, ENCODE | dontBreakLines);

			// GZip?
			if (gzip == GZIP) {
				gzos = new java.util.zip.GZIPOutputStream(b64os);
				oos = new java.io.ObjectOutputStream(gzos);
			} // end if: gzip
			else {
				oos = new java.io.ObjectOutputStream(b64os);
			}

			oos.writeObject(serializableObject);
		} // end try
		catch (java.io.IOException e) {
			e.printStackTrace();
			return null;
		} // end catch
		finally {
			try {
				oos.close();
			} catch (Exception e) {
			}
			try {
				gzos.close();
			} catch (Exception e) {
			}
			try {
				b64os.close();
			} catch (Exception e) {
			}
			try {
				baos.close();
			} catch (Exception e) {
			}
		} // end finally

		// Return value according to relevant encoding.
		try {
			return new String(baos.toByteArray(), PREFERRED_ENCODING);
		} // end try
		catch (java.io.UnsupportedEncodingException uue) {
			return new String(baos.toByteArray());
		} // end catch

	} // end encode

	/**
	 * Encodes a byte array into Base64 notation. Does not GZip-compress data.
	 * 
	 * @param source
	 *            The data to convert
	 * @since 1.4
	 */
	public static String encodeBytes(byte[] source) {
		return encodeBytes(source, 0, source.length, NO_OPTIONS);
	} // end encodeBytes

	/**
	 * Encodes a byte array into Base64 notation. <p/> Valid options:
	 * 
	 * <pre>
	 *    GZIP: gzip-compresses object before encoding it.
	 *    DONT_BREAK_LINES: don't break lines at 76 characters
	 *      &lt;i&gt;Note: Technically, this makes your encoding non-compliant.&lt;/i&gt;
	 * </pre>
	 * 
	 * <p/> Example: <code>encodeBytes( myData, Base64.GZIP )</code> or <p/>
	 * Example:
	 * <code>encodeBytes( myData, Base64.GZIP | Base64.DONT_BREAK_LINES )</code>
	 * 
	 * @param source
	 *            The data to convert
	 * @param options
	 *            Specified options
	 * @see Base64#GZIP
	 * @see Base64#DONT_BREAK_LINES
	 * @since 2.0
	 */
	public static String encodeBytes(byte[] source, int options) {
		return encodeBytes(source, 0, source.length, options);
	} // end encodeBytes

	/**
	 * Encodes a byte array into Base64 notation. Does not GZip-compress data.
	 * 
	 * @param source
	 *            The data to convert
	 * @param off
	 *            Offset in array where conversion should begin
	 * @param len
	 *            Length of data to convert
	 * @since 1.4
	 */
	public static String encodeBytes(byte[] source, int off, int len) {
		return encodeBytes(source, off, len, NO_OPTIONS);
	} // end encodeBytes

	/**
	 * Encodes a byte array into Base64 notation. <p/> Valid options:
	 * 
	 * <pre>
	 *    GZIP: gzip-compresses object before encoding it.
	 *    DONT_BREAK_LINES: don't break lines at 76 characters
	 *      &lt;i&gt;Note: Technically, this makes your encoding non-compliant.&lt;/i&gt;
	 * </pre>
	 * 
	 * <p/> Example: <code>encodeBytes( myData, Base64.GZIP )</code> or <p/>
	 * Example:
	 * <code>encodeBytes( myData, Base64.GZIP | Base64.DONT_BREAK_LINES )</code>
	 * 
	 * @param source
	 *            The data to convert
	 * @param off
	 *            Offset in array where conversion should begin
	 * @param len
	 *            Length of data to convert
	 * @param options
	 *            Specified options
	 * @see Base64#GZIP
	 * @see Base64#DONT_BREAK_LINES
	 * @since 2.0
	 */
	public static String encodeBytes(byte[] source, int off, int len,
			int options) {
		// Isolate options
		int dontBreakLines = (options & DONT_BREAK_LINES);
		int gzip = (options & GZIP);

		// Compress?
		if (gzip == GZIP) {
			java.io.ByteArrayOutputStream baos = null;
			java.util.zip.GZIPOutputStream gzos = null;
			Base64.OutputStream b64os = null;